Communications devices such as radios used by public safety agencies, for example, emergency first responder organizations, include one or more power amplification components, such as, radio frequency (RF) devices that transmit high power energy. The RF devices may be, for example, RF transistors connected to a printed circuit board. One of the consequences of high power transmission is a significant amount of heat is dissipated from the RF devices. This heat must be adequately managed while maintaining electrical performance. Therefore, the RF devices and the connected circuit board structure are typically attached to a heat sink with a soldering material. However, current soldering techniques do not provide a specific and repeatable dimension between an input/output lead plane and a ground flange plane in the RF device, circuit broad, and heat sink assembly. Therefore, there is no reliable platform for repeatable solder attachment of the RF device terminations in the input/output lead plane and the ground flange plane of the RF device, circuit board, and heat sink assembly.
In addition to the RF devices, other components, for example, ceramic components may also be connected to the circuit board. The reliability of the soldering material attaching these components may be affected by the heat sink assembly. Therefore, there is a need to address solder fatigue failure in power cycling by restricting the rigid attachment between the RF device/circuit board structure and the heat sink to an area away from the ceramic components and thereby reduce applied stresses on the ceramic matching component solder joints. This is important for high-power, high-duty cycle infrastructure power amplifiers that are particularly prone to solder joint fatigue failure. Furthermore, there is a need for a soldering technique that is compatible with a high-temperature lead-free solder processing which is a strict requirement for the next generation infrastructure power amplifiers.
In addition, the grounding structure for the RF device and printed circuit board assembly is important because these communications devices have an RF circuit, rather than simply a direct current (DC) circuit. Hence, it is critical to maintain good ground paths for the bottom of the circuit board, as well as, for the RF devices generating power amplification. Current grounding techniques fail to provide optimal RF grounding of the matching circuit input/output transmission lines on the RF devices and circuit broad assembly to the heat sink, i.e., where the RF grounding is as close as possible to the body of RF devices to improve electrical performance. As such, current grounding techniques fail to provide good thermal and grounding paths from the bottom of the RF transistor though the ground flange to heat sink directly below.
Furthermore, there is a need for an integrated circuit board and heat sink assembly that can be easily processed with standard surface mount technology (SMT) processing, such as solder paste stencil printing, part auto-placement and reflow soldering. There is also a need to lower processing cost with a simplified method for attaching the circuit board and heat sink assembly, thereby eliminating the need for the current specialty process capabilities being used at suppliers.
Accordingly, there is a need for an improved method and apparatus of assembling a grounding and thermal management apparatus for a radio frequency device and a matching circuit.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.